Contra Costa

Formed February 18, 1850 (4^th county)

Contra Costa County (1,165,927), Martinez (37,273), Concord (125,411)

The governmental Contra Costa County courthouse was built in 1932 in Neo-Classical Revival style.  It is located at Main and Court streets.  Interstate Highway 680 passes a mile to the east of the courthouse.  Edward Geoffrey Bangs was the courthouse designer.  The building was remodeled in 1966.  A Judicial Center was added in 1986.  There was a 1901 courthouse also in Martinez, which has been the only county seat.  This is now the County Financial Building.  Contra Costa county was formed on February 18, 1850 as an original county.  The 4^th county.  Contra Costa is Spanish for “Opposite Coast.”  Ignacio Martinez, commander of the Presidio of San Francisco provided his name to the county seat. 

Contra Costa County government consists of a sheriff, assessor, controller, and treasurer (executive).  It has 5 Supervisors (legislative.)  Thirty-six Superior Court Judges, clerk, and counsel serve Contra Costa County (judicial.)  The county is located on the northeast side of the San Francisco Bay north and east of Oakland, California.  The San Francisco Bay is the northwest border, the combined Sacramento and San Joaquin rivers’ delta is the northern border, and the San Joaquin River is the eastern border.  The county center is 25.4 miles Southeast of Martinez nearer Clayton.  The county is surrounded clockwise by Solano, Sacramento, San Joaquin, San Francisco, Alameda, Sonoma, and Marin counties.  The county is shaped like a bowl of popcorn leaning slightly to the northwest.  Martinez is west of center and on the northern border of the county.  Concord is located in the north and west of the county center.  Martinez is the county seat and Concord is the largest city.  Martinez is 3.2% of the county population while Concord is 10.8% of the county population.  The county is pronounced CON-TRA COS-TA.  The county seat is pronounced MAR-TEE-NEZ.  

The area of the county is 720 square miles.  It is 51 out of 58 in the state.  It ranks 9 out of 58 in population in the state.  It has a density of 1619.3 persons per square mile making it 7 out of 58 in the state.  Contra Costa County has 84.8% of its population in its incorporated areas.  Interstate Highway 80 enters from Solano County in the north and exits southwest into Alameda County.  Other Interstate Highway loops and connectors also cross the county.  This county is in the San Francisco-Oakland-Fremont MSA.

Walnut Creek